Technical Field
The present invention concerns an adjusting device for adjusting the rotor blade pitch angle of a wind power installation and a method of operating such a device.
Description of the Related Art
Wind power installations are generally known. The type of installation which is mostly widely used at the present time is a so-called horizontal-axis wind power installation in which an aerodynamic rotor driven by the wind rotates substantially about a horizontal axis. In that case in normal operation the axis faces substantially in the direction of the wind and the rotor has at least one and usually three rotor blades which pass over a rotor area which is thus arranged substantially transversely relative to the wind. FIG. 3 shows such a wind power installation.
A pitch angle of each rotor blade relative to the wind can be altered in dependence on the wind speed. In other words, the rotor blade is turned substantially about its longitudinal axis in order to change that pitch angle and thus the afflux flow angle. The pitch angle is frequently also referred to as the angle of attack and adjustment of the pitch angle is frequently referred to as pitching.
To carry out the pitching operation, an adjusting device is used which usually employs an electric drive. The electric drive is operated by means of a power unit which is supplied with electric energy by an electric power supply network.
The power unit for supplying the adjusting drive with power is adapted to the adjusting drive which can also be referred to as the pitch drive. When using a dc motor as the pitch drive the power unit operates as a so-called dc controller. In other words the power unit provides a direct current of the respective current strength which is required for performing the respective adjusting movement.
In the event of failure of the electric supply network there is provided an electric storage means which has stored sufficient energy for the electric drive to adjust the rotor blade into a so-called feathered position. It is to be understood that the electric storage means has that corresponding amount of energy, and thus after a use it is to be charged up again and otherwise care is to be taken to ensure that any self-discharge is compensated by a so-called compensating trickle charge.
Charging of the electric storage means is effected by way of a separate current source which is adapted in its output voltage to the voltage of the electric storage means. In addition there is provided a compensating trickle charge device which performs the described compensating charging operation. It is also adapted in its output voltage to the voltage of the electric storage means and autonomously performs re-charging of the electric storage means in dependence on its charge state.
Such systems are correspondingly complex because they have to perform the described tasks and must function reliably and redundantly.
As general state of the art attention is directed to DE 20 2006 018 866 U1.